Characterization of liquid phase epitaxial GaAs for blocked-impurity-band far-infrared detectors

GaAs blocked-impurity-band (BIB) photoconductor detectors have the potential to become the most sensitive, low noise detectors in the far-infrared below 45.5 cm(-1) (>= 220 mu m). We have studied the characteristics of liquid phase epitaxial GaAs films relevant to BIB detector production, including impurity band formation and the infrared absorption of the active section of the device. Knowledge of the far-infrared absorption spectrum as a function of donor concentration combined with variable temperature Hall effect and resistivity studies leads us to conclude that the optimal concentrartion for the absorbing layer of a GaAs BIB detector lies between 1 x 10(15) and 6.7 x 10(15) cm(-3). At these concentrations there is significant wave function overlap which in turn leads to absorption beyond the Is ground to 2p bound excited state transition of 35.5 cm(-1) (282 mu m). There still remains a gap between the upper edge of the donor band and the bottom of the conduction band, a necessity for proper BIB detector operation. (c) 2004 Elsevier B.V. All rights reserved.